Promise Chaining

Posted at 2016-04-16 Promise Chain

Promise 似乎可以更簡單做到 Chain Of Responsibility

範例
線上sandbox 你可以把 code 複製貼到這裡執行

var discountService = new Promise(function(resolve, reject) {
  let orderPrice = 1000;
  resolve(orderPrice);
});

var dptDiscount = function(orderPrice){
  orderPrice *= 0.9;
  return orderPrice;
};

var bigOrderDiscount = function(orderPrice){
  orderPrice *= 0.95;
  return orderPrice;
};

var vipDiscount = function(orderPrice){
  orderPrice -= 100;
  return orderPrice;
};

let result = discountService.then(function(orderPrice) {
  return dptDiscount(orderPrice);
}).then(function(orderPrice) {
  return bigOrderDiscount(orderPrice);
}).then(function(orderPrice) {
  console.log(vipDiscount(orderPrice));
});

let result2 = discountService.then(function(orderPrice) {
  return vipDiscount(orderPrice);
}).then(function(orderPrice) {
  return dptDiscount(orderPrice);
}).then(function(orderPrice) {
  console.log(bigOrderDiscount(orderPrice));
});

output

1
2

755
769.5

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